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Un ensemble d'habitats de la Tène moyenne à la période augustéenne au sud-ouest de Caen : la fouille de la rue des Longrais à Maltot (Calvados)
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Breakdown elementary mechanisms within controlled nanometer scale electrode gaps: Best Poster Student Award, 36th International Conference on Phenomena in Ionized Gases (ICPIG)
No full textInternational audienceThis study reproduce the deviation from the Paschen's law in controlled conditions, in order to study the underlying elementary processes responsible for the breakdown in sub-micrometer gaps. This clarifies certain discrepancies in the very few experimental results published in the past. The point is also to suggest an empirical approach based on statistical analysis to describe the competition between the different breakdown processes
Site Frequency Spectrum in stationary branching populations
No full textThis paper explores the Site Frequency Spectrum (SFS) in stationary branching populations. We derive estimates for the SFS associated with a sample from a continuous-state branching process conditioned to never go extinct, utilizing a quadratic branching mechanism. The genealogy of such processes is represented by a real tree with a semi-infinite branch, and we compute the expectation of the SFS under the infinitely-many-sites assumption as the sample size approaches infinity. Additionally, we present a continuum version of the SFS as a random point measure on the positive real line and compute the density of its expected measure explicitly. Finally, we derive estimates for the size of the clonal subpopulation carrying the same genotype as the most recent common ancestor of the whole population at a given time
Relaxation-Based In Vivo Discrimination of Oxidized and Reduced States of a Redox-Switchable <sup>19</sup>F MRI Probe
No full textInternational audienceMRI assessment of the tissue redox state is important for revealing and understanding various pathologies, and redox responsive imaging probes capable of generating discrete and quantifiable signals both in their reduced and oxidized forms can provide enhanced detection reliability. The small fluorinated, redox-active FeL1 chelate is a prototype of such agents. L1 forms stable and inert complexes with both Fe2+ and Fe3+ions, and the redox potential of the Fe3+ L1/Fe2+L1 couple (+240 mV vs. NHE) is adapted to biological redox sensing. Fe2+L1 undergoes instantaneous oxidation in the presence of H2O2, and Fe3+L1 is reduced by cysteine, glutathione and ascorbate. Fe2+L1 and Fe3+L1 have very different proton relaxivities (0.1 mM -1 s -1 and 2.83 mM -1 s -1 , respectively, 60 MHz, 298 K), as well as 19F relaxation times (T1 = 71-130 ms; T2 = 60-117 ms and T1 = 2.43 ms; T2 = 1.81 ms, respectively, 400 MHz, 298 K), in accordance with the different paramagnetic relaxation enhancement capacity of the two iron redox states. Upon applying specific MRI pulse sequences adapted to the relaxation rate (RARE for Fe2+L1 and UTE for Fe3+L1, combined with appropriate acquisition parameters), both redox forms are detected in 19F MR phantom images with good sensitivity and signal-to-noise ratios linearly dependent on probe concentration. Fe2+L1 and Fe3+L1 can be readily visualized and unambiguously discriminated based on their 19 F relaxation times in living mice, following intramuscular injection. The possibility to monitor the redox switch in 1 H MRI as well is an additional advantage of this bioresponsive probe
Identification des paramètres d'un modèle hyperélastique par indentation instrumentée et apprentissage par variété
No full textInternational audienceAn identification method based on manifold learning is applied to ascertain parameters of the Mooney–Rivlin hyperelastic model from experimental indentation curves. The methodology is experienced on two different materials, an unfilled natural rubber and a filled silicone rubber. The identifications obtained from indentation experiments are compared with those obtained from representative macroscopic tests, showing a good agreement. As expected, it appears that the methodology is sensitive to experimental variation resulting from factors such as the surface roughness or the presence of fillers in the tested material. Therefore, to control the surface roughness, a surface preparation protocol for the silicone rubber is presented. Moreover, a numerical treatment of the curves is developed to reduce the influence of surface roughness, leading to a significant reduction of the identification dispersion for the roughest tested surface. The impacts of the aforementioned experimental factors are further discussed based on existing literature and the development of a numerical model that reproduces the indentation test on a rough surface
Can fiscal rules improve banking system stability in developing countries?
No full textThis paper investigates the causal impact of fiscal rules on banking system stability in developing countries. Using a panel of 62 developing economies over the period 1990-2020, the authors assess whether adopting a fiscal rule contributes to reducing the level of non-performing loans, a key indicator of banking vulnerability. The analysis relies on entropy balancing to ensure covariates balance between treated and control groups. Results indicate that the adoption of fiscal rules significantly reduces the ratio of non-performing loans, with an average treatment effect of approximately 0.97 percentage points. The study identifies multiple transmission channels-sovereign credit ratings, income inequality reduction, and macroeconomic stabilization-through which fiscal rules indirectly strengthen banking stability. Heterogeneity analysis reveals that the effect varies by the type and duration of the rule and by structural financial characteristics. This research contributes to the literature by extending the role of fiscal rules beyond debt and deficit control, framing them as institutional anchors for financial stability in fiscally and economically vulnerable contexts.</div
Co-constructing and simulating LUCC scenarios for evaluating the sustainability of environmental policies and helping the decision-making over the long term
No full textInternational audienceUrbanization and agricultural intensification are major drivers of biodiversity loss due to multiple stressors, including land artificialization, habitat fragmentation, isolation, and degradation. These land-use and land-cover changes (LUCC) also impact water quality, carbon sequestration, and ecosystem services. Designing Blue and Green Infrastructure Networks (BGINs) has been proposed as a strategic approach to land-use planning that enhances ecosystem services while preserving biodiversity and improving water management. This study focuses on the Couesnon watershed (Brittany, France) within the LTSER Zone Atelier Armorique (https://deims.org/31e67a47-5f15-40ad-9a72-f6f0ee4ecff6). A participatory approach was employed to develop five future LUCC scenarios incorporating BGINs. Narrative descriptions were then used as input for the FORESCEM model to simulate LUCC dynamics (Fig. 1 - Houet et al. 2022). The impacts on biodiversity were assessed by evaluating changes in landscape connectivity for woodlands, grasslands, and wetlands using the model developed by Boussard et al. (2020). Additionally, the effects on water quality and quantity were analyzed under LUCC and RCP8.5 climate change scenarios using the model developed by Álvarez-Cabria et al. (2016). The effectiveness of BGIN policies was assessed by comparing current landscape connectivity (2018) with projected connectivity in 2050 and by estimating future water quality. Results indicate that despite integrating BGINs, the projected impacts on biodiversity (Fig. 2) and water resources could still be significantly negative. Key drivers of future agricultural land-use changes and related environmental impacts include evolving CAP priorities, demographic trends among farmers, and climate change. While BGINs are effective in mitigating urbanization impacts, they may not be sufficient at the landscape scale. This study highlights the necessity of systemic environmental policies that foster synergies among different administrative services involved in land management. The current sectoral (or "siloed") organisation levels remain a barrier to achieving land sustainability goals. While LUCC simulations are designed to assist decision-makers in implementing sustainable policies, we examined whether our results effectively support local stakeholders in the Couesnon watershed. We conducted 14 public meetings involving nearly 150 participants, including farmers, policymakers, land and resource management professionals, and students. Surveys and interviews conducted during the meetings and 6 to 12 months later revealed that while scenario-based approaches can influence decision-making, their impact requires time to materialize (Rigo and Houet 2023, Rigo et al. 2024). These findings underscore the need for further research and the importance of effectively communicating scientific insights to support the understanding, monitoring, and sustainable management of socio-ecological systems within the critical zone
Nonlinear Resonant Interactions of Radiation Belt Electrons with Intense Whistler-Mode Waves
No full textInternational audienceThe dynamics of the Earth's outer radiation belt, filled by energetic electron fluxes, is largely controlled by electron resonant interactions with electromagnetic whistler-mode waves. The most coherent and intense waves resonantly interact with electrons nonlinearly, and the observable effects of such nonlinear interactions cannot be described within the frame of classical quasi-linear models. This paper provides an overview of the current stage of the theory of nonlinear resonant interactions and discusses different possible approaches for incorporating these nonlinear interactions into global radiation belt simulations. We focus on observational properties of whistler-mode waves and theoretical aspects of nonlinear resonant interactions between such waves and energetic electrons. We consider only sufficiently energetic particles, which can be treated as test particles and do not have a significant feedback to the waves. The review covers two main regimes of nonlinear resonant wave-particle interactions: the regime of long wave-packets, historically better studied, and the regime of short wave-packets, actively investigated more recently based on refined spacecraft observations
Search for continuous gravitational waves from known pulsars in the first part of the fourth LIGO-Virgo-KAGRA observing run
No full textInternational audienceContinuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of General Relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO--Virgo--KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering the single-harmonic and the dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the asymmetry in the neutron star mass distribution. For the single-harmonic emission model, 29 targets have the upper limit on the amplitude below the theoretical spin-down limit. The lowest upper limit on the amplitude is for the young energetic pulsar J0537-6910, while the lowest constraint on the ellipticity is for the bright nearby millisecond pulsar J0437-4715. Additionally, for a subset of 16 targets we performed a narrowband search that is more robust regarding the emission model, with no evidence of a signal. We also found no evidence of non-standard polarizations as predicted by the Brans-Dicke theory
Comprehensive Physicochemical and Biological Analysis of Hydroxyapatite/Dextran Powders before and after Immersion in Kokubo Solution
No full textInternational audienceUnderstanding the behavior of biomaterials under physiological conditions is essential for the development of new materials for implants and bone regeneration. This study addresses the critical need to evaluate how exposure to simulated body fluid (SBF) affects hydroxyapatite (HAp) and dextran-coated hydroxyapatite (HApDx) nanoparticles, which are widely considered for biomedical applications due to their bioactivity and biocompatibility. Structural, morphological, and surface property changes induced by SBF immersion were systematically investigated for the first time using advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and fractal and Minkowski functional analyses. The results revealed that SBF immersion significantly influenced both HAp and HApDx, leading to reduced crystallite sizes, surface smoothening, and enhanced structural homogeneity. FTIR and FT-Raman spectra indicated subtle structural modifications, while SEM and AFM analyses confirmed the formation of a biomimetic apatite layer and a decrease in surface roughness. These changes are indicative of improved bioactivity, suggesting enhanced potential for osteoconductivity and cellular interaction. Biological evaluations using MG63 osteoblast-like cells demonstrated favorable cell viability and adhesion across 24, 48, and 72 h, particularly for the samples immersed in SBF. AFM further confirmed that surface modifications supported the cell attachment and proliferation. Overall, our findings underscore the importance of SBF exposure in enhancing the physicochemical and biological performance of HAp-based materials, reinforcing their promise for biomedical applications